Reaction of phenylurea and N-trimethylsilyl-N′-phenylurea with vanadocene and N-bromosuccinimide

Article abstract of DOI:10.1023/B:RUGC.0000016022.68917.bd

Phenylurea and N-trimethylsilyl-N′-phenylurea react with vanadocene (Cp₂V) in toluene to give N-(η⁵-cyclopentadienyl) vanadio-N′-phenylurea as a major product and Cp₂VN=C=O and aniline as by-products. The reaction of N-trimethylsilyl-N′-phenylurea with N-bromosuccinimide in THF produces, instead of expected N-phenylureidosuccinimide and bromotrimethylsilane, succinimide and N-(p-bromophenyl)-N-trimethylsilylurea which hydrolyzes to form (p-bromophenyl)urea.

Full text of DOI:10.1023/B:RUGC.0000016022.68917.bd

Russian Journal of General Chemistry, Vol. 73, No. 10, 2003, pp. 1557 1560. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 10, 2003,
pp. 1650 1653.
Original Russian Text Copyright
2003 by Gordetsov, Zimina, Kulagina, Moseeva, Kurskii, Lopatin.
Reaction of Phenylurea and N-Trimethylsilyl-N -phenylurea
with Vanadocene and N-Bromosuccinimide
A. S. Gordetsov, S. V. Zimina, N. V. Kulagina,
E. M. Moseeva, Yu. A. Kurskii, and M. A. Lopatin
Nizhny Novgorod State Medical Academy, Nizhny Novgorod, Russia
Received March 12, 2002
Abstract Phenylurea and N-trimethylsilyl-N -phenylurea react with vanadocene (Cp2V) in toluene to
give N-( 5-cyclopentadienyl)vanadio-N -phenylurea as a major product and Cp2VN=C=O and aniline as by-
products. The reaction of N-trimethylsilyl-N -phenylurea with N-bromosuccinimide in THF produces, instead
of expected N-phenylureidosuccinimide and bromotrimethylsilane, succinimide and N-(p-bromophenyl)-N-
trimethylsilylurea which hydrolyzes to form (p-bromophenyl)urea.
Proceeding with research into the synthesis and
chemical properties of new biologically and catalyti-
cally active organoelement derivatives of phenylurea
[1 4], we synthesized the first organovanadium de-
rivative, N-( 5-cyclopentadienyl)vanadio-N -phenyl-
urea (I). The reaction of Cp2V with phenylurea (evac-
uated sealed ampule, toluene, 70 100 C, 48 h, reagent
ratio 1:1) gave compound I as a major product (yield
70%) as greenish-brown fine crystals. By GLC we
also detected in the reaction ampule hydrogen and
cyclopentadiene.
dium oxygen coordination bonds, like organovana-
dium sulfo derivatives we obtained previously [5, 6].
H
H
H
H
Ph N C N V Cp
Ph N C N
V Cp
O
O
O
Cp V N C N Ph
A
H
H
B
With a silicon-containing analog of phenylurea,
N-trimethylsilyl-N -phenylurea, the yield of compound
I (the reaction was performed in THF) increased to
94%. Instead of hydrogen, hexamethyldisilane formed
(GLC data).
The reaction in more rigid conditions (120 C, more
than 70 h) provided, along with the major product,
much bis-( 5-cyclopentadienylvanadio) isocyanate.
The amount of the latter increased with increasing
reaction time. At the same time, the isocyanate con-
centration no longer increased when the reaction
temperature was raised further (thermolysis began).
Unambiguous evidence for isocyanate formation was
provided by the observation in the IR spectra of the
reaction mixture of the following characteristic ab-
Cp2V(SH)
PhNHC(O)NHR
[PhNHC(O)NHVCp2]
1/2R2
PhNHC(O)NHVCp
CpH
I
(1)
t
1
Cp2VN=C=O
sorption bands, cm : 2210 (N=C=O), 3100, 1005,
PhNH2
800 (isocyanate Cp) [7]. From the filtrate we isolated
aniline.
If R = H or Me3Si and SH is a protic solvent, the
IR spectrum of compound I contains the following
It should be noted that aniline and organoelement
isocyanates (Bu3SnN=C=O, Me3SiN=C=O) were
earlier found among reaction products of phenylurea
with the corresponding tin- and silicon-containing
reagents [4].
1
principal absorption bands, cm : 3310 (N H), 1645
(C=O), 1590, 1530, 1500, 830, 740, 710, 590 (Ph),
1010, 1005, 810 (Cp).
The ESR spectra of urea I (toluene or THF) or re-
action mixtures show no signals of paramagnetic
vanadium complexes (including, the parent vanado-
cene). It thus can be suggested that compound I can
exist as monomer A or dimer B with strong vana-
On contact with air the absorption bands of
Cp2VN=C=O quickly disappear, whereas the charac-
teristic absorption bands of compound I practically
do not change their intensity. However, on prolonged
1070-3632/03/7310-1557$25.00 2003 MAIK Nauka/Interperiodica

1558
GORDETSOV et al.
exposure to air (about 2 months) compound I is
oxidized to phenylureidovanadium oxide (II), whereas
when boiled in water it undergoes hydrolysis into the
parent phenylurea.
Unlike reaction (1), the reaction of N-trimethylsilyl-
N -phenylurea with N-bromosuccinimide gave un-
expected results. It was found that the reaction begins
already as the reagents are mixed in THF without
heating and is accompanied by strong heat release.
To complete the reaction, the mixture was refluxed
(66 C) for 24 h. The solvent was then removed to
leave a thick sticky reddish substance containing,
according to the elemental analysis, primarily N-(p-
O2(H2O)
I
PhNHC(O)NHV=O
CpH
II
H2O (100 C)
(2)
PhNHC(O)NH2.
bromophenyl)-N -trimethylsilylurea
(III)
whose
The IR spectra of compound II show no Cp ab-
hydrolysis in air in ether resulted in isolation of up to
50% of (p-bromophenyl)urea (IV) and succinimide
(yield 74%).
sorption bands but acquire a vanadium oxygen ab-
1
sorption band at 1035 cm [6].
O
O
C
H2C
N Br
PhNHCNHSiMe3 +
H2C
C
O
O
O
O
C
C
H2O
H2C
H2C
p-BrC6H4NHCNH2
+ p-BrC H NHCNHSiMe
3
N Br
6
4
(Me3Si)2O
III
IV
O
O
O
O
O
C
C
C
H2C
H2C
H2C
H2C
H2O
(3)
N NHCNHPh
N OH + PhNHCNH2
Me3SiBr
C
O
O
The IR spectra of compound III contain the fol-
lowing principal absorption bands, cm : 3390, 3280,
200, 245 nm, respectively. The band near 200 nm is
1
*
formed by the
transition in the hydrocarbon
3180, 1600, 1580 (NH), 1650 (C=O), 3090, 1540,
1060, 1000, 805, 750, 705, 490 (Ph), 1480, 1460
(C N), 1240, 850 (M3Si). The lack in the IR spectra
of compound IV of M3Si absorption bands provides
further evidence for its purity.
The 1H NMR spectrum of compound IV (200 MHz;
acetone-d6), , ppm: 5.56 br.s [2H, H2NC(O)],
7.34 7.49 m (AA BB , 4H, C6H4), 8.25 br.s [1H,
C(O)NHPh].
skeleton and in not characteristic. The broad band near
*
240 nm is a superposition of bands formed by n
*
(C=O) and
(benzene ring) electronic transitions.
Whereas the carbonyl absorption band is only slightly
affected by substituents, the benzene band is shifted
bathochromically on introduction of substituents into
the ring. For the reaction products, the absorption
band not only shifts from 238 to 245 nm, but also it
gets broader and acquires a shoulder at 255 nm,
implying that the reaction products contain bromine
in the ring.
In the NMR and IR spectra of the reaction mixtures
we found signals assignable to the second product of
reaction (3), succinimide [ , ppm: 2.68 s (4H, CH2),
9.98 br.s (1H, NH)]. The starting materials were not
found.
1
According to our findings supported by UV, H
NMR, and IR spectral data, as well as DTA, the reac-
tion does not take way characteristic of similar
chemical systems and involving formation of trime-
thylhalosilane and corresponding ureide [3]. This is
proved, for example, by the lack of Me3SiBr among
In the UV spectra of the starting compounds and
reaction products we found maxima at 200, 238 and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 10 2003

REACTION OF PHENYLUREA AND N-TRIMETHYLSILYL-N -PHENYLUREA
the reaction products (is not detected even with an
1559
indicator), of signals of phenylurea and N-hydroxy-
succinimide in the 1H NMR spectra {reference
PhNHC(O)NH2, , ppm: 4.68 br.s [2H, H2NC(O)],
6.47 br.s [1H, C(O)NH], 7.1 7.4 m (5H, C6H5);
reference N-hydroxysuccinimide, , ppm: 2.56 s (4H,
CH2), 4.65 (1H, NOH)}.
endo
270.4
t
212.8
Compound IV was also subjected by DTA analysis.
The themoanalytical curve (see figure) reveals two
endothermic transitions: weak low-temperature at
212.8 C and principal high-temperature at 270.4 C.
The first maximum corresponds to the melting point
of compound IV and the second, to the melting point
of N,N -bis(p-bromophenyl)urea. The DTA data give
evidence for the opinion of Kurzer [8] that monoaryl-
substituted ureas undergo an extremely fast thermal
transformation into diaryl-substituted, which is res-
ponsible for ill-defined melting points of these com-
pounds prepared also other methods. Thus, as noted
in [8, 9], the reported melting points of compound IV
vary from 220 to 278 C, which corresponds to mix-
tures of mono- and sym-disubstituted ureas. Accord-
ing to DTA, compound IV, as well as its diaryl-sub-
stituted analog are present among products of the reac-
tion of N-bromosuccinimide with phenylurea.
exo
150
200
250
300
t, C
Thermoanalytical curve of (p-bromophenyl)urea (IV).
solution changed color from violet characteristic of
vanadocene to greenish-brown characteristic of the
major reaction product, and a precipitate formed.
Filtration followed by washing with hot toluene gave
1.10 g (70%) of N-( 5-cyclopentadienylvanadio)-N -
phenylurea (I). Found, %: C 57.45; H 4.93; V 20.35.
C12H12N2OV. Calculated, %: C 57.38; H 4.82; V
20.28. Cyclopentadiene and hydrogen were detected
by GLC. Upon exposure to air for 2 months com-
pound I converted to phenylureidovanadium oxide
(II), dark brown fine crystals. Found, %: C 42.07; H
3.98; V 24.97. C7H7N2O2V. Calculated, %: C 41.60;
H 3.49; V 25.21.
In conclusion it may be noted that N-trimethylsilyl-
N -phenylurea fails to react with Ph3BiCl2, Ph4SbCl,
tris( -bromomethyl) isocyanurate, and tris( , -di-
bromopropyl)isocyanurate under conditions similar to
those of the reactions studied or even more rigid
conditions (for instance, prolonged heating in an
evacuated reactor).
Reaction of vanadocene with N-trimethylsilyl-
N -phenylurea was performed in a similar way with
0.58 g of Cp2V and 2.08 g of N-trimethylsilyl-N -
phenylurea in 40 ml of THF to obtain 0.75 g (94%)
of compound I. Cyclopentadiene and (Me3Si)2 were
detected by gas chromatography in the filtrate.
EXPERIMENTAL
All chemical manipulations with organovanadium
compounds were performed in evacuated devices or
in sealed evacuated two-section ampules with a glass
filter. The IR spectra were obtained on Specord IR-75
and Specord M-80 instruments for suspensions in
mineral oil between KBr or ZnSe plates. The ESR
spectra were recorded on a Bruker-ER-200D-SRC
Reaction of N-bromosuccinimide with N-tri-
methylsilyl-N -phenylurea.
N-Bromosuccinimide,
3.55 g, was added to 100 ml of a stirred solution of
4.15 g of N-trimethylsilyl-N -phenylurea in THF.
After heat release no longer observed (maximal tem-
perature 50 C), the mixture was heated at 100 C for
4 h. Fine white crystals formed and were filtered off.
According to DTA and IR data, it contained 1.47 g
(74%) of succinimide. The solvent was removed from
the filtrate, and the residue was heated in a vacuum
(3 4 mm) at 60 C for 1 h to obtain 3.67 g (64%) of
N-(p-bromophenyl)- N -trimethylsilylurea (III), sticky
reddish amorphous material. Found, %: C 42,63; H
5.30; Br 25.91. C10H15BrN2OSi. Calculated, %: C
41.82; H 5.26; Br 27.82. Hydrolysis of the resulting
material in wet ether gave 2.14 g (50%) of (p-bromo-
phenyl)urea, mp 212.8 C {published data [8]: mp
220 C.
1
spectrometer at 9.4 GHz. The H NMR spectra were
measured on a Bruker DPX-200 spectrometer (200
MHz, acetone-d6). The UV spectra were obtained on
a Perkin Elmer Coleman-575 spectrometer. Chro-
matography of CpH was performed by the procedure
in [5] and of silicon-containing compounds, by the
procedure in [7]. N-Trimethylsilyl-N -phenylurea was
synthesized by the procedure in [2].
Reaction of vanadocene with phenylurea. A
mixture of 1.12 g of Cp2V and 0.84 g of phenylurea
was heated in 40 ml of toluene for 48 h at 100 C. The
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GORDETSOV et al.
beleva, S.E., Kulagina, N.V., and Pereshein, V.V., Izv.
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